The long-term objectives of this agreement will be to provide the scientific community with more information concerning the usefulness of idiotype vaccines and the role of idiotype regulation of immune responses. Initially, monoclonal antibodies (MoAb) to Eimeria maxima sporozoites (AB-1) will be produced. MoAb (AB- 2) will subsequently be produced that will recognize and react with AB-1. Chickens will be inoculated with one of the following treatments: 1) sporozoites, 2) AB-1, 3) AB-2, and 4) saline as a control. Serum antibody titers from uninoculated and inoculated chickens will be determined to sporozoite antigens in an ELISA. Subsequently, challenge studies will be performed in chickens with the following test groups: 1) pre-treatment of chickens with either sporozoite, AB-1 or AB-2, 10 days post-treatment birds will be challenged with oocysts, 2) no pretreatment, challenge with sporozoites, and 3) saline challenge. This portion of the study will be evaluated by analysis of feces for viable oocysts and necropsy examination of the intestinal tract for lesions caused by a patent E. maxima infection. Future proposals concerning this area will involve the network theory of idiotype regulation of immune responses.